1. Field of the Invention
This invention concerns conductive coatings used, generally, in the electronics industry. The invention more particularly concerns an electrically conductive, electroplated, material covering a surface of a polymer element, where the electroplated material does not delaminate from the surface of the polymer element after subsequent high temperature soldering.
2. Discussion of the Background
Conductive coatings are well-known in the art which are also known as conductive inks. Conductive inks have many favorable characteristics, in that the compositions may include metals such as silver, copper, lead or tin to provide electrical conductivity. The conductive inks also may include adhesives such as polymeric binders which provide for solderability and adhesion strength. Conductive inks have been used for many applications, including applying conductive traces to printed circuit boards. The related art shows the application of conductive ink by silk screen printing onto a non-moldable insulating baseboard substances, such as FR4 or glass epoxy.
Polymers, which are commonly referred to as plastics, are known in the art which have characteristics, including high mechanical strength, durability, toughness, chemical resistance and high temperature performance. Liquid crystal polymers (LCPs) offer these characteristics, while providing the advantage of all moldable plastics. LCPs are able to withstand temperatures as high as 520.degree. fahrenheit before deforming. It is an object of the present invention to combine the high temperature and moldable properties of plastics such as LCP with the quick and convenient process of printing with conductive inks.
Other applications require an overall coating of conductive material around an object. Typically, the object is made of a polymer so as to be injection moldable. One quick way of applying an overall coating is by way of an electroplating process. Such a solution was achieved in the automotive industry with the introduction of metallized plastics such as acrylanitrile butadiene styrene (ABS) which is a plastic material having an outer coating of a metal alloy. The metal coating typically includes a base coating of a copper alloy, with a second layer of a nickel alloy covering the copper alloy layer, and a third layer of a chrome alloy covering the nickel alloy layer. The use of metallized plastics in applications such as automotive bumpers and automotive interior compartment decorative trim elements works well for the intended purpose.
Recently, attempts have been made to solder a metallized plastic part to a printed circuit board so as to make electrical contact between the printed circuit board and the electrically conductive coating of the metallized plastic part. The result being that the two components were soldered together. However, the electrically conductive material covering the plastic part delaminated or blistered away from the surface of the plastic part. Such delamination is not acceptable in the electronics industry since the bond between the two components is not adequate. The bond between the two components is subject to tearing and thus subject to loss of electrical continuity between the two components.
Therefore, there is a need for a metallized plastic part which is solderable and which does not delaminate.